On Nov 29, 4:45 pm, "Y.Porat" <
y.y.po...@gmail.com> wrote:
>
> PD you are not donr withme so easy
> i am not a little child
> so i will ask you in a different way :
>
> why modern physics is talking about
> ; ''a single photon''' interfering with itself
>
> WHAT IS THAT ''SINGLE PHOTON THAT THEY ARE TALKING ABOUT ??
>
> how do they get it and how do the define it ??
>
> you see
> my criticism is not only personally against
> it is about those things that you are parroting !!
>
> TIA
> Y.Porat
> ----------------------------
(a) I think, moving forward, you should disentangle your ego from this
discussion and humbly accept the role of student. A statement like "I
am not a little child" is very revealing because it shows that you
feel somehow *slighted*. But this is a discussion foremost about
helping you to understand observed physical facts. Don't connect your
ego with the facts that you know: because learning something new is an
opportunity, not an insult.
(b) The photon is a conceptual tool we use to understand a truly
massive number of different physics experiments. The basic idea is
this: "Light is made of 'atoms' or lumps in the sense that, if you
turn down the intensity of light far enough, the light comes in
discrete units of energy called photons. Each photon has an energy
related to its frequency by Planck's constant E = h f."
Planck derived this relation when he was studying perfect thermal
radiation -- what's known as "black-body radiation." Einstein
solidified its interpretation when he pointed out that it offered an
elegant explanation of the photoelectric effect -- for this discovery,
he was given a Nobel prize.
The modern picture goes very far beyond this. For example, discrete
energy 'bands' are the understood basis for the modern semiconductor
technology working in your computer, and atomic spectra -- the
discrete energy levels of atoms -- are today used to figure out how
fast distant galaxies are moving away from us. Excited atoms emit
photons of distinct frequencies and can only be excited by light at
the same frequency. It also explains, for example, why sunlight can
give you skin cancer while indoor light does not, and discrete
energies also come out in things like positron emission tomography --
PET scans, where it's actually very important that *two* photons are
emitted in *opposite* directions when a positron annihilates with an
electron. (You need two to emit a lot of energy while preserving
conservation of momentum.)
The full laws of electrons and photons -- the principles that allow
such *particles* to display *wavy* interference effects -- was worked
out by Feynman and Schwinger among others, and is called Quantum
Electrodynamics. For further understanding of the concept of photons,
I refer you to Feynman's New Zealand lectures, available here:
http://vega.org.uk/video/subseries/8
When we speak about single photons interfering with themselves, we are
speaking of interference effects which work even when you reduce the
photon bursts to clear one-at-a-time resolutions. Similar wavy
interference effects happen with electrons in what are called
"Aharanov-Bohm" rings, where an electron can either take path A or
path B to get to the other side: at some magnetic fields you see *no*
current due to the electron-waves interfering as they go down this
path, but raise the magnetic field more and you can see the current
double, too. You can get the same effects with the so-called "double-
slit experiment", even when the light-transport is reduced to one
photon emitted per second.
As he has said, the rate is very different from the frequency. The
frequency of light, you might know, corresponds to its color. So you
can have a very weak blue light: photons with a lot of "kick", but
coming very infrequently. Or you can have a very strong red light:
photons with much less "kick", but many more of them coming more
frequently.
I hope that all helps? Cheers.
== Drostie ==